Constructed wetlands have been extensively applied for treating drinking water sources and other water bodies that are not severely polluted due to their low construction and operation costs. In this regard, microbial fuel cells (MFC) could potentially achieve both energy generation and wastewater purification, though the construction cost is high. Based on the bio-electrochemical theory, a novel device of the integrated vertical flow constructed wetland (IVCW) embedded with MFC (IVCW-MFC) was designed and built for treating the slightly-polluted source waters with relatively high nitrogen and low carbon, where denitrification was usually hindered. Both water purification performance and electrical characteristics were examined in this system. It was observed that the maximum output voltage and power density could reach 777 mV and 8.05 mW·m^-2, respectively, when the external resistance was 6000 Ω. With a better denitrification effect, the system exhibited a more effective removal of chemical oxygen demand (COD) and nitrate. The maximum efficiency of total nitrogen (TN) removal was as high as 97.35%, while the average removal efficiency was around 70%, even with a load of TN, 3.3 mg/L on average, in the influent. Furthermore, the macrophytes grew normally in the constructed wetland without any influence.